SpringBoot

不学无数—SpringBoot入门Ⅱ

SpringBoot入门Ⅱ

Posted by 不学无数 on September 2, 2018

SpringBoot

1.Starters

Starters是一套技术，是什么技术呢？是SpringBoot整理出来，人们经常要用的技术。有了starters人们在想要使用这些技术的时候，就不用扒之前的老代码将那些依赖啊或者配置的都拷贝过来，只需要加上SpringBoot提供的依赖就行，它自动会进行依赖管理。例如，如果你想在SpringBoot项目中集成JPA，那么只需要在引入jar包的地方加上spring-boot-starter-data-jpa即可，SpringBoot会自动将其和其他所依赖的包加载进项目中。

所有SpringBoot提供的Starters命名都有一套规则，spring-boot-starter-*，其中的*就是你想要引用的技术的名称。

下面列一些Starters

名称 描述
spring-boot-starter SpringBoot的核心，其中提供了自动配置的支持，日志，以及YAML
spring-boot-starter-activemq 提供对于ActiveMq的使用的支持
spring-boot-starter-amqp 对于Spring AMQP和RabbitMQ的支持
spring-boot-starter-aop 对于Spring面向切面编程的支持
spring-boot-starter-web 初始化关于Web启动的一些东西，另外支持RESTful，支持SpringMvc，使用tomcat为默认的内嵌容器

在这就简单介绍这几个Starters，想看具体介绍的可以参考SpringBootg官方文档

2.自定义启动页面

在项目启动的时候，在打印日志的上面会有一个图像，这个就是启动的时候自动加载的。就像下面这样初始图像是这样的。

 .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.4.7.RELEASE)

2018-07-16 10:18:03.591  INFO 4737 --- [           main] c.e.F.FirstSpringBootApplication         : Starting FirstSpringBootApplication on hupengfeideMacBook-Pro.local with PID 4737 (/Users/hupengfei/mygit/FirstSpringBoot/out/production/classes started by hupengfei in /Users/hupengfei/mygit/FirstSpringBoot)
2018-07-16 10:18:03.595  INFO 4737 --- [           main] c.e.F.FirstSpringBootApplication         : No active profile set, falling back to default profiles: default
2018-07-16 10:18:03.659  INFO 4737 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@7fbdb894: startup date [Mon Jul 16 10:18:03 CST 2018]; root of context hierarchy

如果想要更改的话也简单，就是在资源文件的下面添加一个banner.txt文件，然后将想要的展示的信息填写进去就行了，项目启动的时候回自动去加载这个文件。

___.                                                  .__
\_ |__  __ _____  _____ __   ______  _  ____ __  _____|  |__  __ __
 | __ \|  |  \  \/  /  |  \_/ __ \ \/ \/ /  |  \/  ___/  |  \|  |  \
 | \_\ \  |  />    <|  |  /\  ___/\     /|  |  /\___ \|   Y  \  |  /
 |___  /____//__/\_ \____/  \___  >\/\_/ |____//____  >___|  /____/
     \/            \/           \/                  \/     \/
2018-07-16 10:19:53.941  INFO 4745 --- [           main] c.e.F.FirstSpringBootApplication         : Starting FirstSpringBootApplication on hupengfeideMacBook-Pro.local with PID 4745 (/Users/hupengfei/mygit/FirstSpringBoot/out/production/classes started by hupengfei in /Users/hupengfei/mygit/FirstSpringBoot)
2018-07-16 10:19:53.945  INFO 4745 --- [           main] c.e.F.FirstSpringBootApplication         : No active profile set, falling back to default profiles: default
2018-07-16 10:19:54.015  INFO 4745 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@15a04efb: startup date [Mon Jul 16 10:19:54 CST 2018]; root of context hierarchy

此时就会发现启动的图像变了。将字母生成字符画

如果不想打印任何的图像信息，那么只需要在资源文件下的配置文件中设置即可。

spring:
    main:
        banner-mode: "off"

3.定制SpringApplication

如果默认的SpringApplication不符合自己想要的配置结果，那么可以进行定制化的配置。例如像上一章节的如果像关闭启动的图像信息，上一章节是在配置文件中进行关闭，那么也可以在启动的main文件中进行定制化关闭。

public static void main(String[] args) {
    SpringApplication app = new SpringApplication(MySpringConfiguration.class);
    app.setBannerMode(Banner.Mode.OFF);
    app.run(args);
}

对于完整的SpringApplication配置选项，可以参考SpringApplication文档

4.Spring事件的监听

除了一些正常的Spring的事件监听，例如ContextRefreshedEvent,有时候也有可能需要一些特殊的事件的监听。下面就列出一些特殊的事件，例如你想在项目启动的时候做一些事情，或者是项目启动失败的时候做一些事情。这些SpringBoot都提供有相应的功能。

事件名称 何时被调用
ApplicationEnvironmentPreparedEvent 环境准备好，Spring容器被创建之前
ApplicationPreparedEvent 在项目启动refresh之前
ApplicationReadyEvent 在项目启动成功之后
ApplicationFailedEvent 在项目启动时发生异常

可以看到每个事件被触发时的时间。

I AM ApplicationEnvironmentPreparedEvent

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.4.7.RELEASE)

2018-07-16 14:44:37.110  INFO 5397 --- [           main] c.e.F.FirstSpringBootApplication         : Starting FirstSpringBootApplication on hupengfeideMacBook-Pro.local with PID 5397 (/Users/hupengfei/mygit/FirstSpringBoot/out/production/classes started by hupengfei in /Users/hupengfei/mygit/FirstSpringBoot)
2018-07-16 14:44:37.114  INFO 5397 --- [           main] c.e.F.FirstSpringBootApplication         : No active profile set, falling back to default profiles: default
I AM ApplicationPreparedEvent
2018-07-16 14:44:37.168  INFO 5397 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@528c868: startup date [Mon Jul 16 14:44:37 CST 2018]; root of context hierarchy
2018-07-16 14:44:38.299  INFO 5397 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2018-07-16 14:44:38.309  INFO 5397 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2018-07-16 14:44:38.310  INFO 5397 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.15
2018-07-16 14:44:38.391  INFO 5397 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2018-07-16 14:44:38.391  INFO 5397 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1227 ms
2018-07-16 14:44:38.530  INFO 5397 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2018-07-16 14:44:38.539  INFO 5397 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-07-16 14:44:38.540  INFO 5397 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-07-16 14:44:38.540  INFO 5397 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2018-07-16 14:44:38.540  INFO 5397 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2018-07-16 14:44:38.851  INFO 5397 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@528c868: startup date [Mon Jul 16 14:44:37 CST 2018]; root of context hierarchy
2018-07-16 14:44:38.929  INFO 5397 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto java.lang.String com.example.FirstSpringBoot.FirstSpringBootApplication.home()
2018-07-16 14:44:38.933  INFO 5397 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2018-07-16 14:44:38.933  INFO 5397 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2018-07-16 14:44:38.960  INFO 5397 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-16 14:44:38.960  INFO 5397 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-16 14:44:38.995  INFO 5397 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-16 14:44:39.197  INFO 5397 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-07-16 14:44:39.272  INFO 5397 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
I AM ApplicationReadyEvent

代码如下，这是使用了内部类的写法，也可以自己建一个类实现ApplicationListener然后传入所建的类即可。

public static void main(String[] args) {
        SpringApplication app = new SpringApplication(FirstSpringBootApplication.class);
        app.addListeners((ApplicationListener<ApplicationEnvironmentPreparedEvent>) event -> {
            System.out.println("I AM ApplicationEnvironmentPreparedEvent");
        });
        app.addListeners((ApplicationListener<ApplicationPreparedEvent>) event -> {
            System.out.println("I AM ApplicationPreparedEvent");
        });
        app.addListeners((ApplicationListener<ApplicationReadyEvent>) event -> {
            System.out.println("I AM ApplicationReadyEvent");
        });
        app.run(args);
    }

5.ApplicationRunner和CommandLineRunner

有时候在业务中会碰到这些需求，要求在容器启动的时候执行一些内容，例如读取配置文件，数据库的连接等等。SpringBoot提供了两个接口为我们解决这些问题。一个是ApplicationRunner另一个是CommandLineRunner

5.1 CommandLineRunner接口

@Component
public class AppliRunner implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("--------CommandLineRunner---------"+Arrays.asList(args));
    }
}

然后在设置里面设置Program arguments

然后项目启动就可以发现输出了这些信息

2018-07-16 16:56:08.216  INFO 5745 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-07-16 16:56:08.278  INFO 5745 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
--------CommandLineRunner---------[aaa,bbbb]
2018-07-16 16:56:08.282  INFO 5745 --- [           main] c.e.F.FirstSpringBootApplication         : Started FirstSpringBootApplication in 2.557 seconds (JVM running for 3.227)
Disconnected from the target VM, address: '127.0.0.1:59214', transport: 'socket'

5.2 ApplicationRunner接口

ApplicationRunner接口和CommandLineRunner接口的不同之处在于参数的不同，ApplicationRunner接口的传参是ApplicationArguments，是对参数的一层封装。而CommandLineRunner接口的参数是可变的String。

@Component
public class AppliRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.println("-----ApplicationRunner----"+args.getOptionNames());
        System.out.println("-----ApplicationRunner----name:"+args.getOptionValues("name"));
        System.out.println("-----ApplicationRunner----age:"+args.getOptionValues("age"));
    }
}

在启动设置中设置参参数如下

然后在启动的时候可以发现如下的参数

2018-07-16 17:15:16.502  INFO 5825 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-07-16 17:15:16.564  INFO 5825 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
-----ApplicationRunner----[name, age]
-----ApplicationRunner----name:[不学无数]
-----ApplicationRunner----age:[23]
2018-07-16 17:15:16.568  INFO 5825 --- [           main] c.e.F.FirstSpringBootApplication
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